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Appendix VI.


separate the levers N N and compel them to bite the collet tube P,
thus pulling the split cone Q against the hollow cone R on the
mandrel tube s, and thereby fastening or chucking the stock bar.
A leftward motion of M releases the levers N N, which are then
compelled by springs to approach and lie on the tube P; and the
latter, being freed, is acted on by the spring u, relieving the grip
at Q. The stud v similarly actuates the collar x, and gives move-
ment to the stock tube w, the split collar y nicely gripping the
stock. When w moves leftward the stock is in chuck, and a new
position is taken up between w and the stock; but the rightward
motion of w takes place only when the chuck Q is freed, and the
stock is therefore carried forward for a new series of operations.
It will be noticed then that one complete article is machined at
each revolution of the cam shaft D in Fig. 939.

Fig. 941 shews an elevation and sectional plan of the cam-
shaft driving gear. The pulley A turns the worm shaft B either
directly or through epicyclic gear, so that quick or slow rotation
of the cams is provided at will; the slow motion being needed
when cutting, and the fast when no actual work is being done,
thus saving time in operation. When driving slowly the pinions
c c are carried round the fixed wheel D and the free wheel E, the
latter having one or two teeth more than D ; and if clutch F be
engaged the worm shaft receives this slow rotation. By releasing
F and putting clutch G in connection, the spur wheels turn
solidly and cause B to rotate at the same rate as pulley A. To
effect these changes automatically a large disc H . has a series of
lugs, such as j, fixed upon its rim in agreed positions, and these
at the proper times strike a pin K on the bell crank lever L, thus
compelling the rack lever M to move the shaft B to right or left,
and engage clutches F or G alternately, a quick and positive action
being secured by the spring stud N. These movements may be
prevented when required by releasing the catch P, and the shaft B
can then be turned by hand wheel Q through clutch n, which is
ordinarily kept out of action by the spring s.

The turret head is given in Fig. 942 by a sectional elevation
and plan. The turret A is mounted so as to rotate on stud c
when required, and carries in five holes as at B the necessary
turning tools for the operations to be performed. The turret